parent-child margin collapse

Hey guys .

talking about parent- child margin collapse which is a better hack ?

.parent {
    padding-top: 1px;
    margin-top: -1px;
}

or

.parent {
    overflow:auto
}

i am asking because when it comes to containers collapsing due to floats inside them the

.parent {
    overflow:auto
}

has side effects in macs .